(1) Field of the Invention
The invention relates to a linear actuator, at least including a stator that is placed within a cartridge-like casing, a bearing seat for mounting a rotor with an antifriction bearing, the bearing seat in assembled condition being located behind the stator, a spindle that on the drive side thereof is together with the rotor designed as motion transformer to transform the rotary motion into a translatory motion and a flange that closes the casing on the output side of the linear actuator, the flange equipped with an anti-rotation locking device for the spindle output side that penetrates the flange.
(2) Description of Related Art
Generally, the axial, or face-side, respectively, closure of linear actuators, particularly of linear stepper motors and the necessary support of thrust forces are achieved by laser or spot welding of the stator packet that is placed within the casing and the flange that is placed on the output side of the linear stepper motor. Examples of prior art are the motors of the series 20DAM made by DANAHER, the motors of the series PFCL25/35 made by NPM and the motors of the series LSP15/25/35 made by NANOTEC.
Other motor manufacturers such as NMB (PL25), SAIA (UBL/ELD) or FDK (VLL30) weld the stator packet and connect the flange by means of bending tongues.
The HIS company mounts the flange to the stator packet of the series 20000 motors instead of using bending tongues, by material caulking at the casing, with additionally welding the stator packet.
Solutions by the applicant are also known where the ball bearing is axially locked by ultrasonic welding and the flange attached to the stator by using bending tongues. Connection of two plastic parts can instead of using the ultrasonic welding process also be made by rotary friction welding.
The traditional solution to screw the stator and flange together is chosen by HSI and MOONS, with the hybrid stepper motors made in square design that requires more installation space. In the rotary motors by NMB the stator packet is also fixed by over-molding with a plastic material; in a motor of the applicant the flange is attached to the stator by clinching.
A particular disadvantage of the above mentioned connection methods is, first, the high capital cost for installing the expensive production lines with the associated production steps. Second, the fixtures and machines for the frequently used laser, spot or ultrasonic welding processes need very intensive maintenance, furthermore being susceptible to faults under certain environmental conditions.